The present invention relates to an apparatus for the linear acceleration of electrons, particularly for intraoperative radiation therapy.
Intraoperative radiation therapy is a therapeutic method used in treating deep neoplasms and consists in delivering a single intense dose of radiation onto a tumoral mass, preventing the dose from affecting the surrounding healthy tissues.
Its field of utilization ranges from surgically inoperable tumors, to tumoral residues after partial surgical exeresis, to a tumoral bed after full surgical removal. In this manner, by delivering the dose of radiation directly onto the tumor or onto the macroscopic or microscopic tumoral residue, it is possible to spare the peritumoral healthy tissues that are instead affected by radiation in conventional radiation therapy with external beams.
Currently there is growing interest in the use of this therapeutic method for a wide range of tumors, particularly those affecting the abdomen, the pelvis, and the chest. The association of this therapy with surgery and with conventional radiation therapy allows to considerably improve local control of advanced-phase neoplasms.
Large electron accelerators, which allow to treat a patient both with an electron beam and with X rays, have been successful in the execution of this intraoperative radiation therapy. Use of electron-bee therapy offers high versatility in treating tumoral residues after surgical removal as well as tumoral masses deemed inoperable.
However, large electron accelerators have some drawbacks which can limit their use.
A first drawback can be found in their high cost.
A second drawback is the considerable bulk of the apparatus.
The real drawback of electron accelerators, however, resides in the intense irradiation produced, which cannot be confined with simple movable panels, and therefore in the consequent need for heavily shielded work sites.
Special radiation-therapy bunkers are therefore built for this purpose with concrete walls one or two meters thick. The shielding of radiation-therapy sites is governed by specific safety regulations.
For intraoperative radiation therapy, the patients are transferred under anaesthesia from the operating room to the radiation-therapy bunker, under constant monitoring; the subsequent steps of the process and, usually, the final step of the surgery being performed on the patient take place in said bunker. Only in rare cases the operating rooms are located directly in a bunker so as to simultaneously act as a radiation-therapy room as well.
The need to transfer the patient to a location other than the operating room causes problems linked to the risks of transferring the patient under anaesthesia and to the time that elapses between surgical exeresis and subsequent radiation therapy.
It is furthermore necessary to strictly schedule each operation according to the availability of access to the radiation-therapy site, and this increases the working time requirements and reduces the number of patients who can utilize this radiation therapy.
Furthermore, in current electron accelerators the irradiation unit (known as "radiating head"), the modulator, and the components for therapy are assembled in a single block that is difficult to move due to its weight and size.
This does not allow the radiating head to be placed precisely in space and to be moved in a flexible manner, so that the electron beam treats the entire tumoral mass involved, despite the irregular shape that said mass may have.
In order to avoid this drawback, with the linear electron accelerators used so far it is necessary to increase the cross-section of the radiation beam, with greater problems in terms of shielding and damage to healthy surrounding tissues.
Finally, the difficulty in moving the radiating head makes it impossible to vary the dose of emitted radiation for each point of the tumoral mass, so as to administer the dose prescribed by the physician to each area.